Catheter tracking system

1. A catheter tracking system for locating and tracking a catheter head with reference to a part of the human or animal body, said catheter tracking system comprising: a plurality of spaced apart transducers, at least one of which is disposed on a catheter and at least two others of which are disposed at predetermined reference points; and a signal processing unit coupled to the plurality of spaced apart transducers and arranged to selectively enable individual ones of said plurality of spaced apart transducers to operate as either a transmitter or a receiver, and to energize at least one of the transmitters to generate at least one transmitted signal which is detected by at least one of said receivers, a time of flight of the at least one transmitted signal generated by the at least one transmitter and received by the at least one receiver being indicative of a distance between said at least one transmitter and said at least one receiver, and times of flight between the at least one transducer disposed on the catheter and the at least two other transducers disposed at said predetermined reference points providing an indication of the location of the catheter with reference to said reference transducers; wherein, the at least one transmitted signal has a predetermined waveform; the signal processing unit compares the at least one transmitted signal generated by said at least one transmitter with a signal representative of the transmitted signal received by the at least one receiver, and determines the time of flight of the at least one transmitted signal based on a result of said comparison; and said comparison is performed using cross-correlation of pairs of transmitted and received signals, with the received signal being shifted in time, a maximum peak of energy resulting from the cross-correlation being detected, and the time of flight being determined from a time shift corresponding to a temporal position of maximum cross-correlation energy.

2. A catheter tracking system as claimed in claim 1, wherein said at least one signal generated is acoustic.

3. A catheter tracking system as claimed in claim 1, wherein said acoustic signal is ultrasonic.

4. A catheter tracking system as claimed in claim 1, wherein said predetermined waveforms generated from each of said plurality of transducers are different with respect to each other, said difference facilitating contemporaneous detection of said signals, thereby facilitating determination of said catheter head location at a faster rate.

5. A catheter tracking system as claimed in claim 4, wherein each of said predetermined waveforms generated from each of said plurality of transducers is different with respect to a change in frequency with respect to time.

6. The catheter tracking system as claimed in claim 1, wherein said transmitted signal comprises one of: a signal which is shifted in frequency with respect to time in a predetermined manner; and digital data in the form of an M-sequence.

7. A catheter tracking system for locating and tracking a catheter head with reference to a part of the human or animal body, said catheter tracking system comprising: a plurality of spaced apart transducers, at least one of which is disposed on a catheter and at least two others of which are disposed at predetermined reference points; and a signal processing unit coupled to the plurality of spaced apart transducers and arranged to selectively enable individual ones of said plurality of spaced apart transducers to operate as either a transmitter or a receiver, and to energize at least one of the transmitters to generate at least one transmitted signal which is detected by at least one of said receivers, a time of flight of the at least one transmitted signal generated by the at least one transmitter and received by the at least one receiver being indicative of a distance between said at least one transmitter and said at least one receiver, and times of flight between the at least one transducer disposed on the catheter and the at least two other transducers disposed at said predetermined reference points providing an indication of the location of the catheter with reference to said reference transducers; wherein, the at least one transmitted signal has a predetermined waveform; the signal processing unit compares the at least one transmitted signal generated by said at least one transmitter with a signal representative of the transmitted signal received by the at least one receiver, and determines the time of flight of the at least one transmitted signal based on a result of said comparison; predetermined waveforms generated from each of said plurality of transducers are different with respect to each other, said difference facilitating contemporaneous detection of said signals, thereby facilitating determination of said catheter head location at a faster rate; and each of said predetermined waveforms generated from each of said plurality of transducers comprises a different one of a set of substantially orthogonal digital sequences.

8. The catheter tracking system as claimed in claim 7, wherein said comparison is performed using cross-correlation of pairs of transmitted and received signals, with the received signal being shifted in time, a maximum peak of energy resulting from the cross correlation being detected and the time of flight being determined from a time shift corresponding to a temporal position of maximum cross-correlation energy.

9. A catheter tracking system for locating and tracking a catheter head with reference to a part of the human or animal body, said catheter tracking system comprising: a plurality of spaced apart transducers, at least one of which is disposed on a catheter and at least two others of which are disposed at predetermined reference points; and a signal processing unit coupled to the plurality of spaced apart transducers and arranged to selectively enable individual ones of said plurality of spaced apart transducers to operate as either a transmitter or a receiver, and to energize at least one of the transmitters to generate at least one transmitted signal which is detected by at least one of said receivers, a time of flight of the at least one transmitted signal generated by the at least one transmitter and received by the at least one receiver being indicative of a distance between said at least one transmitter and said at least one receiver, and times of flight between the at least one transducer disposed on the catheter and the at least two other transducers disposed at said predetermined reference points providing an indication of the location of the catheter with reference to said reference transducers; wherein, the at least one transmitted signal has a predetermined waveform; the signal processing unit compares the at least one transmitted signal generated by said at least one transmitter with a signal representative of the transmitted signal received by the at least one receiver, and determines the time of flight of the at least one transmitted signal based on a result of said comparison; and said signal processing unit operates to determine a frequency dependent transfer function between transmitting and receiving transducers, providing information about the media through which said signal has propagated.

10. A catheter tracking system as claimed in claim 9, wherein said signal processing unit further operates to determine absorption coefficient data representative of said media through which said signal has propagated, and advantageously adjusts said distance measurements consequent upon said time of flight of said signal in combustion with said absorption coefficient data.

11. A method of tracking a catheter head with reference to a part of the human or animal body, said method comprising: disposing at least two of a plurality of spaced apart reference transducers at predetermined positions with a reference to the human or animal body; inserting a catheter with at least one transducer disposed proximate the catheter head, inside the human or animal body; generating and transmitting at least one signal from the plurality of reference transducers or from the at least one transducer disposed on said catheter, said transmitted signal including a predetermined waveform; detecting the at least one signal, including the predetermined waveform, with the at least two reference transducers or the at least one transducer disposed on said catheter, whereby a time of flight between the at least one transducer disposed on the catheter and the at least two of the plurality of spaced apart reference transducers at predetermined positions gives an indication of the location of said catheter with reference to the reference transducers; comparing the at least one transmitted signal generated by the at least one transmitter with a signal representative of the transmitted signal received by the at least one receiver; and determining the time of flight of the at least one transmitted signal based on a result of said comparison; wherein said comparison is performed using cross-correlation of pairs of transmitted and received signals, with the received signals being shifted in time, a maximum peak of energy resulting from the cross-correlation being detected, and the time of flight being determined from a time shift corresponding to a temporal position of maximum cross-correlation energy.

12. A method of tracking a catheter head as claimed in claim 10, wherein the steps of comparing said generated and said received signals is done by cross-correlation of pairs of transmitted and received signals.

13. A method of tracking a catheter head as claimed in claim 12, further comprising generating said predetermined waveforms which differ from each other, said difference facilitating contemporaneous detection of said signals, thereby facilitating the determine of said catheter head location at a faster rate.

14. The method as claimed in claim 11, wherein said transmitted signal comprises one of: a signal which is shifted in frequency with repect to time in a predetermined manner; and digital data in the form of an M-sequence.